Typically folding character displays for electronic typewriters, personal word processors or portable computers have been designed to cover the keyboard when placed in the down position. The brake mechanisms designed heretofore for the these types of displays have been designed to accommodate the specific needs of a flip-up display that covers the keyboard. To move the display from the down position covering the keyboard to an upright viewing position often involves a relatively large angle of movement. The displays are generally long enough to cover a large portion of the keyboard so the arm length is long and the proportioned lever type force from the weight of the display is relatively large. Brake mechanisms of this type include rachet type hinges and indexed position hinges as well as frictional force devices. Using frictional force brake mechanisms has advantages including continuous adjustment of viewing positions, smoother movement of the display and are less noisy than other types of brake mechanisms.
U.S. Pat. No. 4,730,364 entitled "Data Processor Flush Hinge Assembly" shows a hinge assembly that includes a brake assembly that holds the display in a desired position between 90.degree.-180.degree. relative to the down position of the display. A hinge assembly of this type would be useless for any display that did not need to be pivoted more than 90.degree. relative to the down position of the display.
U.S. Pat. No. 4,781,422 entitled "Adjustable Clutch Mechanism" shows a pivotable display and clutch mechanism comprising a series of rings and a tension spring. The tension spring applies a constant pressure causing a frictional force between the rings thus holding the display in position The user must overcome this applied force while the screen is brought from a down position into a range of useful viewing positions, so a trade off exists between ease of movement of the screen for the user and adequate frictional force to hold the display. The mechanism is a delicate cooperation of a spring, bolts, nuts, spacers, and numerous rings and plates. It is easy to see how a brake mechanism with so many parts could wear easily and fail If the mechanism did fail it would be extremely difficult to fix and would make the computer extremely cumbersome and difficult to use.
U.S. Pat. No. 4,790,504 entitled "Display Support Mechanism" shows an disengageable brake mechanism for holding the display in a desired position. The brake mechanism comprises a lug portion which is turned to deform a socket portion of the display and thereby hold it in place. A brake mechanism of this type is cumbersome in that it requires the user to disengage the lug portion, set the display in a desired position and reengage the lug portion. It is not practical for frequent adjustment and repeated closing and opening of a flip up display.